A controversial metal shredding operation on the north Minneapolis riverfront wants permission to pump more pollution into the air, saying it can't meet limits it agreed to 13 years ago.

Northern Metal Recycling wants to raise selected pollution limits, loosen restrictions on what goes into the shredder, and reduce the frequency of pollution testing at its scrap recycling yard near the west end of the Lowry Avenue Bridge.

Opponents ranging from area legislators to the City Council and Park Board to the National Park Service are lining up against the shredder's request. State Reps. Phyllis Kahn and Joe Mullery, both Minneapolis DFLers, termed the firm's proposal "an outrage" in a letter to state regulators, adding that it is "an enormous step in the wrong direction."

Northern, owned by an English firm, bought the business yard in 2007 from American Iron & Supply, which battled for years at City Hall and the Legislature and in court to install a metal shredder. It started operation in 2009, and soon afterward violated its emission limits for mercury by 32 percent as well as emitting three times the fine particles that its permit allowed.

In August 2010, the company agreed to pay a $15,000 fine after the Minnesota Pollution Control Agency (MPCA) cited it for air quality violations and submitted what the agency described as a plan to come into compliance.

But opponents raised alarms this month when they found out that the company is proposing to do so by allowing a ninefold increase in the particle levels that the plant is allowed to emit. The company's compliance plan said it can't meet the particle limits the state set in a 1998 permit, that it has installed the best available technology to control particles and that meeting the state limit is technologically impossible.

The company also argues that its emissions fall within the national standards for air quality.

"When the agency issued the permit in 1998, they overstated what was needed to protect human health and the environment," said Mike Hansel, a vice president at Barr Engineering, a consultant to Northern.

For the smallest particulate measured, it's only a hair below the standard. Other modeling estimates that the proposed higher emissions would add between 4 and 9 percent to existing health risks for acute and chronic respiratory hazards or cancer.

The data also estimates one additional cancer death per 100,000 people but only in the unlikely scenario that a person lived and ate garden produce grown right at the Northern Metal fence line, for 70 years.

Small particles are worrisome from a health standpoint because the smaller the particulate, the more likely it is to enter lungs or even the bloodstream, causing serious health issues, according to the U.S. Environmental Protection Agency.

The proposed permit would set a new limit on the finest particles. The MPCA has refused Northern Metals' bid to triple its mercury emissions.

Opponents of the permit changes have asked for more study and opportunity for public comment.

State Sen. Linda Higgins, DFL-Minneapolis, told regulators that stringent regulation is needed because the closest neighborhoods are home to low-income people who suffer disproportionately from asthma, respiratory disease and birth defects.

Also objecting was Superintendent Paul Labovitz of the Mississippi National River and Recreation Area, within which the facility sits. He said the facility's site on the riverside makes its impact especially sensitive. Although shredders also operate within the national park area at Newport and Anoka, both are at least one-quarter mile off the river.

The shredder is located in an area with the city's heaviest industrial zoning, although the Minneapolis Park and Recreation Board counts six parks within an eight-block radius. Long-term city plans call for transforming the site to parks and housing.

"Standards should be increased -- not decreased -- in these circumstances," Bruce Chamberlain, an assistant parks superintendent, told the MPCA.

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